rockafellow



April 22, 1958 IN SERIES WITH AN ACTUATING MEANS Filed Aug. 21, 1956 CONDUCTOR FOR CONTROLLED I OUTPUT AL 22 ruermm POTEN'TIAL /9 C/RCU/TPY /z 24 V (Z i f J o/voucrofi FOR 23 5/45 POTE/Vf/AL IN VEN TOR.

United States Patent CONTROL CIRCUIT HAVING IINITIATION SWITCH IN SERIES WITH AN ACTUAT- ING MEANS Stuart C. Rockafellow, Plymouth, Mich, assignor to Robotron Corporation, Detroit, Mich., a corporation of Michigan Application August 21, 1956, Serial No. 605,274 3'Clairns. l. 250-21 This invention relates to a control circuit for electric valves having an initiation switch in series with actuating means for rendering the valve conductive and,more particularly, relates to improved circuitry for use in a sequencing circuit in which the initial conduction of an electric valve is effected by closing thecathode circuit thereof, rather than by removing a biasing potentialfrom the control grid of the valve. I

Controls for carrying out electrical sequencing functions 'are used for 'a variety of purposes, such as the control of electric resistance welding machines. Conventionally, such controls employ a series of thyratrons, and the conduction of at least some of the thyratrons is initiated by removing a biasing potential from the control grid thereof. This technique, while effective for performing the sequencing functions, has been found to be somewhat undesirable from a safety and/or a maintenance standpoint. Consequently, it is desirable to provide Improved circuitry for eiiecting conduction of the thyratrons and other types of electric valves in which an initiation switch in series with the potential source initiates the conduction of the valve. 7

In devising such circuitry, a problem of particular importance involves the provision of means to maintain the circuit for the valve in condition for conducting during the entire sequencing operation and during subsequent sequencing cycles, if necessary, even though the valve itself might be non-conductive at certain intervals due to the imposition of a biasing potential on the control grid thereof as the result of functioning of other elements of the circuit. Further, it is desirable to provide a means to maintain the circuit for the valve in conductive condition as long as the valve is conducting, even though the initiating switch may open while the valve is conducting.

Accordingly, it is a principal object of this invention to provide improved circuitry for controlling the initiation of conduction of an electronic valve.

It is a further object of this invention to provide improved circuitry, as aforesaid, in which conduction of the valve is controlled by an initiation switch, said switch being in series with the source of potential for the valve.

It is a further object of this invention to provide improved circuitry, as aforesaid, wherein the initiation switch controls the operation of a relay, the relay contacts being in the cathode circuit of the valve and said relay being energizable by said switch independently of the valve.

It is a further object of this invention to provide improved circuitry, as aforesaid, wherein said relay once energized by said initiating switch, will remain energized so long as said valve remains conductive.

Other objects and advantages of the invention will be apparent to those acquainted with circuitry of this type upon reading the following description and inspecting the accompanying drawing, which is a circuit diagram of a preferred embodiment of the invention.

In general, the invention provides a relay, whose winding is connected at one of its ends to a first side of an 2,831,973 Patented Apr. 22, 1958 A. C. source and in parallel with the anode circuit of the valve, and whose contacts are in the cathode circuit of said valve. A conductor, having a switch and a rectifier, is connected to the other end of thefrelay winding and to asecond side of the A. C. source. The rectifier is sensed to permit current flow from the winding to said second side of the A. C. source. A second conductor, including a rectifier, connects the relay winding to the anode of the valve, the rectifier being sensed to permit current flow from said winding to said anode.

,Detailed description I A pair of line conductors 10 and 11 areconnected to a suitable source of A. C. potential. An electric valve 12 ode of valve 12 is connected by conductor 15 through relay contacts 18 to the line conductor 11. l

A relay 16 has one end of its winding 17 connected to line conductor 10. The other end of the winding17is connected 'to junction point 19. A conductor 21, having a rectifier 22' therein, connects junction points 14 and 19. Rectifier 22'is "sensed to permit current flow from junction point 19 to junction point 14.

A conductor-23 is connected to junction point 19 and thence through rectifier 24 and switch 25 to line conductor 11. The rectifier 24 is sensed to permit current flow from junction point 19 to line conductor 11. The switch 25 is herein shown to be of the manual push-button type. It is to be understood, however, that otherv types of switches, including further electrical circuitry, can be used as the switch, as desired or required.

A conductor 26 is connected to the control grid of valve 12 and may be in turn connected to further circuitry 27, which may be further sequencing circuitry, or other circuitry, as desired, for imposing a biasing potential onto the grid for blocking conduction of valve 12 at the desired time.

It will be'understood that windings 13 and 17 will be shunted by suitable means, such as capacitors 28 and 29, for holding the coils energized during the alternate half cycles in which no current flows thereflirough.

Operation conduction of valve 12, there will be no effect on the conduction of valve 12 because the circuit existing from valve 12 and conductor 15 to line conductor 11 maintains the winding 17 of therelay 16 energized. The relay 16 will thus be locked in" until such time as the valve 12 stops conducting, which may, for example, occur at the end of the pulse being at a given moment supplied to the valve 12, or which may result from the application of a biasing potential to the control grid of valve 12 from further circuitry 27 via line conductor 26. Further, so long as switch 25 is closed, the relay 16 will be energized and the contacts 18 closed, regardless of the condition of valve 12. Thus, relay 16 will be locked in" 3 either by the switch 25 or, once the valve 12 conducts, by the valve 12.

While only a single embodiment of the invention is shown for illustrative purposes, it will be appreciated that the invention is capable of wide application in a variety of situations, other than the situation particularly, although schematically, illustrated herein. Accordingly, the hereinafter appended claims are to be interpreted as applicable to said variety of other applications, except as said claims may by their own terms expressly require otherwise.

I'claim:

l. A control circuit for anjelectric valve, said valve having an anode, a cathode, and a control grid, the combination including: a source of alternating potential; a load connected to the anode of said valve and to, one side of said source; a relay having a winding; a first rectifier, the; winding; of said relay and said first rectifier being in series and connected, inparallel with said load, said first rectifier being sensed to permit current flow from said winding tosaid anode; said relay having contacts connected in series between said cathode and the other side of said source; a conductive means connected from the other side of said source to said winding; a switch in said conductive means adjacent said other side of said source; a second rectifier in said conductive means adjacent said winding, said second rectifier being sensed to permit current flow from said winding to said other side of said source.

2. A control circuit for an electric valve, said valve having an anode, a cathode, and a control grid, the combination including: a source of potential; a load connected. to the anode of said valve and to one side of said source; a relay having a winding and contacts, one end of the winding of said relay being connected to said one side of said source, the contacts of said relay being connected between said cathode and the other side of said source; a first rectifier connected to the other end of said winding and to said anode, said first rectifier being sensed to permit flow of current from said winding to said anode; a second rectifier connected to the other end of said winding; a switch connected between said second rectifier and said other side of said source, said second rectifier being sensed to permit current flow from said winding to said other side of said source.

3. A control circuit for an electric valve, said valve having an anode, a cathode, and a control grid, the combination including: a source of alternating potential; a relay having a Winding and contacts, the winding of said relay being connected to one side of said source and to a first junction point; a load connected to said one side of said source and to a second junction point; conductive means, including; a first, rectifier, connecting said first and second junction points, saidfirst rectifierbeing sensed to permit current flow from said first junction point to said second junction point; a-conductor connecting said second junction point to said anode; means connecting the contacts of said relay'to said cathode and to the other sideof said, source; a second rectifier connected to said first junction point; a second conductor connected to said second rectifier and to the other side of said source; a switch in said second conductor; said second rectifier being sensed to permit current flow from said first junction point to said other side of said-source.

Referencesv Cited in the file of this patent UNITED STATES PATENTS 2,454,168 Hartwig Nov. 16, 1948 

